SATA : Computer Hardware Buyers’ Glossary

SATA (Serial ATA) pronounced say´-tah. This is the faster successor to the older ATA (Advanced Technology Attachment) IDE (Integrated Drive Electronics) drives, now called PATA (Parallel ATA) SATA-1 transfers 150 megabytes per second. SATA2 transfers 3 GBits/Sec. SATA3 transfers 6 GBits/Sec. The term SATA-3 is confusing, do they mean 6 Gb/s SATA-3 or 3 Gb/s SATA-2? The trend is to specify the speed. To use 6 Gb/s SATA you need your controller and hard disk to be 6 Gb/s SATA. If you mix slow and fast SATA controllers and drives it works, but runs at the slow speed.

SATA drops the shared bus of PATA, giving each device a dedicated cable and dedicated bandwidth. SATA cables are narrow with only 7 conductors. Oddly the delicate SATA power connectors have a whopping 15 pins, to deliver 3.3V, 5V and 12V.

You might wonder why a serial connection would be faster than a parallel one. Does not parallel have more wires to transfer data? Yes, they it does, but the signals all must arrive at exactly the same time. To ensure that, they slow down the rate of signalling.